 |
|
Time-gated imaging is an exciting new detection technique which allows the observation of fluorescent particles within biological media without the autofluorescent background present in all organic samples.
At the centre of this technique is a special class of camera known as an intensified CCD camera. In this camera a photcathode screen converts incoming light to electrons, which are then accelerated down metal capillaries, where they collide with the walls and set off an avalanche of electrons. At the far end of the tubes these electrons excite small phosphor screens, and are thus converted back to photons which are detected on image sensors, with each tube linking directly to each pixel. This intensifier has two benefits; firstly it greatly amplifies small signals, but also it only amplifies the light when there is a voltage applied to the cathode tubes. Through precise electronics it is possible to control the time and duration of the applied voltage down to the level of single nanoseconds. In the full setup the camera is coupled to a laser so it can view the fluorescence from a sample at a given time after the laser pulse. In this way it is possible to directly record the decay spectrum of different fluorophores. Further to this, nanoparticles such as quantum dots have longer decay times than that of the chemicals within living cells. Therefore by opening the camera sometime after the laser pulse, the background light has decayed but the quantum dots are still visible, thus background free images can be taken.
For more information on this project, please contact A/Prof A. Zvyagin. |
|
 |
